My bro has a '92 Burb with a TBI 5.7 in it. From what I remember him telling me, he can start it and it will run fine for just a few minutes and then it will idle rough and miss out and smell like it running real rich. There is also a loud squeeling noise coming from the throttle body. He can unhook the vacumm line to the map sensor and it will idle fine. He replaced the map sensor because of the codes, but it still won't idle right. He also replaced the cap and rotor. .